This Lymphocyte Center Grant is designed to support the basic research programs in cellular immunology and immunogenetics of several investigators in the Department of Pathology at Harvard Medical School. We feel that by integrating these research projects administratively, while still preserving their identities scientifically, we achieved several important aims which were not optimized under the previous system of individual funding. Thus, a) We will achieve a greater usage of common equipment facilities and personnel in a more economical way under the category of shared services. b) We can build more effectively, finance, and maintain such unique resources as 1) the precious inbred H-2 congenic and recombinant strains, allotype congenic strains which are maintained in our animal facility under the supervision of Dr. Dorf and which are available for the work of all the investigators in this project as well as outside investigators; 2) a biochemical laboratory headed by Drs. Mescher and Springer, two exceptionally gifted students of Dr. Strominger, where the T cell factors, macrophage products and H-2 gene products will be characterized in collaboration with the respective concerned investigators. c) We can increase the interactions, collaborations and magnify our productivity many folds. Examples of such fruitful collaboration in the past or planned cooperation n the futuue between members of this program are too numerous to describe in detail. Such collaborative studies are presently pursued between Dr. Benacerraf's group and Dr. Dorf, Dr. Unanue, Dr. Mescher, between Dr. Unanue and Dr. Dorf, Dr. Mescher and Dr. Ault to mention only a few of the ongoing projects.